A concise total synthesis of (+/-)-bakkenolide A by means of an intramolecular Diels-Alder reaction

(+/-)-Bakkenolide A was prepared in five steps from ethyl 4-benzyloxyacetoacetate by sequential alkylations with tiglyl bromide nd cis-5-bromo-1,3-pentadiene, followed by an intramolecular Diels-Alder reaction as the key step. The known 7-epibakkenolide A and novel 10-epi- and 7,10-diepibakkenolide A stereoisomers were obtained as minor byproducts.